Variable coordinating activity of sulfur in silver(I) complexes with thiophene based N1-substituted thiosemicarbazones: First case of thiopheneyl-thione sulfur bridging in a dinuclear complex

Abstract

Thiophene-2-carbaldehyde/acetaldehyde-N1-substituted thiosemicarbazones{R1R2C2 = N3- N(H)-C1(=S)N1HR; R1, R2, R : C4H3S, H, Me, Httsc-NMe; C4H3S, H, Et, Httsc-NEt; C4H3S, H, Ph, Httsc-NPh; C4H3S, Me, Et, Hattsc-NEt} and furan-2-carbaldehyde-N-ethyl thiosemicarbazone (C4H3O, H, Et, Hftsc-NEt) were reacted with silver(I) halides/silver(I) acetate in presence of triphenylphosphine in organic solvents. These reactions yielded a series of dinuclear [Ag2(μ-Br)2(κ1-S-Httsc-NEt)2(PPh3)2] ⋅2MeOH 1, [Ag2Cl2(κ1-S- Httsc-NPh)2(μ-S,S-Httsc-NPh)2] 2, [Ag2Cl2(μ-S-Hftsc-NEt)2(κ1-S-Hftsc-NEt)2] 4, [Ag2(μ3-N3,S-ttsc-NMe)2(Ph3P)2] ⋅2(CH3)2CO 5, [Ag2(μ3-N3,S-attsc-NEt)2(Ph3P)2] ⋅0.5(CH3)2CO 6and mononuclear [AgBr (κ1-S-Httsc-NPh)(PPh3)2] ⋅ MeCN 3 complexes, all of which have been characterized using analytical techniques, IR and NMR spectroscopy, and X-ray crystallography. Thio-ligands bind in neutral form in complexes 1-4 and in anionic form in complexes 5-6. Further, the sulfur donor atoms have shown variable coordination modes in complexes, namely, κ1-S in 1 and 3; κ1-S, μ-S in 4; κ1-S, μ-S,S (thiopheneyl-thione) in 2 and μ3- N3, S in 5 and 6. Tertiary-phosphine (PPh3) showed dual function of ligation/de-ligation towards silver(I) chloride during the synthesis of complexes 2 and 4. The bridge bonding of Httsc-NPh in 2 through thiopheneyl ring sulfur and thione sulfur is unprecedented in metal-thiosemicarbazone chemistry. [Figure not available: see fulltext.]